Pertaining to the open ocean environment. Divided into five distinct depth regions called the epipelagic, mesopelagic, bathypelagic,abyssopelagic and hadopelagic zones. {Figure}.

pH

A measure of acidity or alkalinity.

Photoautotrophic

Pertaining to photoautotrophy. Synonymous with phototrophic. Compare to chemoautotrophic.

Photoautotrophy

Synonymous with photosynthesis. Compare to chemoautotrophy.

Photosynthesis

The biological synthesis of organic material using light as an energy source. Plants convert carbon dioxide and water, in the presence of chlorophyll and light energy, into carbohydrate food and oxygen. Synonymous with photoautotrophy. Compare tochemosynthesis.

Photosynthetic

Pertaining to photosynthesis. Compare to chemosynthetic.

Phototrophic

Synonymous with photoautotrophic.

Phylum

The second highest level of taxonomic classification containing one or more Classes forming a subgroup of a Kingdom. The plural of Phylum is Phyla.

Phytodetritus

Particulate matter derived from phytoplankton and plants.

Phytoplankton

Microscopic plant plankton that are the primary producers in the oceans, obtaining their energy through photosynthesis. Compare tozooplankton.

Pinnacle

A small seamount, smaller than a knoll. Definitions vary, but usually includes features that extend up to 250m or 500m from the seabed. {Figure}.

Plankton

The plants or animals that live in the water column, incapable of moving against a current. Includes larval stages of benthic and pelagicorganisms, phytoplankton (in surface waters), zooplankton, jellies and other drifting or weakly swimming organisms. Planktonicorganisms can de divided into holoplankton and meroplankton depending on how much of their life cycle they spend as plankton.

Marine segmented worms. Some are planktonic although most are benthic. The dominant component of the macrofauna. Synonymous with Polychaete.

Polychaete

Synonymous with Polychaeta.

Polychlorinated Biphenyl

A group of toxic organic compounds that persist in the environment for a long time. Often abbreviated to PCB.

Polymetallic Nodule

One of the mineral resources of the Area consisting of any deposit or accretion of nodules on, or just below, the surface of the deep seabed, which contain manganese, nickel, cobalt and copper. Also called manganese nodules and ferromanganese nodules.

Polymetallic Sulphide

One of the mineral resources of the Area consisting of any deposit of sulphide minerals, formed through hydrothermal activity, which contain concentrations of metals including, inter alia, copper, lead, zinc, gold and silver. These deposits include both active sulphidesand inactive sulphides. They may occur on seamounts, mid-ocean ridges or back-arc ridges exposed on the seafloor or as buried deposits.

POM

Particulate Organic Matter

PON

Particulate Organic Nitrogen.

Porcupine Abyssal Plain

An abyssal plain in the North Atlantic Ocean, west of North Europe. It is approximately the size of the European land mass. Abbreviated to PAP.

ppb

Parts per billion.

ppm

Parts per million.

ppt

Parts per thousand

PRA

Preservation Reference Area

Preservation Reference Area

Synonymous with Preservation Reference Zone. Abbreviated to PRA.

Preservation Reference Zone

Areas representative of the mine site in which no mining shall occur to ensure representative and stable biota of the seabed in order to assess any changes in the flora and fauna of the marine environment caused by mining activities. Compare to Impact Zone andImpact Reference Zone. Synonymous with Preservation Reference Area. Abbreviated to PRZ

Primary Consumer

A heterotrophic organism that feeds directly on a primary producer (autotroph). Synonymous with herbivore. Compare to primary producer and secondary consumer.

Primary Producer

Synonymous with autotroph. Compare to primary consumer and secondary consumer.

Primary Production

Amount of organic material produced from inorganic material by primary producers in a given area in a given period of time.

Prokaryote

Cells or organisms lacking a true nucleus, usually having their DNA in a single molecule and not organized in chromosomes. Compare to eukayote.

Prospecting

The search for mineral deposits in the Area, including estimation of the composition, sizes and distributions of such deposits and their economic values, without any exclusive rights. Compare to exploitation and exploration.

Protozoa

Unicellular heterotrophic animals.

PRZ

Preservation Reference Zone.

Pycnocline

A layer of water in which there is a steep gradient in density with depth. It separates the well-mixed surface waters from the dense waters of the deep ocean. Density of the water is a function of temperature, salinity and, to a lesser extent, pressure. Compare tohalocline, nutricline and thermocline.